Consider a hollow aluminum sphere (assume 1 cm diameter, 1 mm wall thickness, filled with and surrounded by air) placed in a uniform magnetic field (assume 10-20 mT). Are there any realistic circumstances in which the magnetic field in the internal volume of the sphere is increased, rather then decreased?
This is not a homework question. One of the answers below says that aluminum is paramagnetic, and would shield the internal volume of the sphere from the magnetic field. It is also known that some common aluminum alloys (e.g. 6061) contain up to 1% ferrous metal. Could this magnetization of the sphere generate a field that exceeds the shielding? What is the likely size of that field?